Abstract: Objective:Extraction and purification alkaloids from fruit shell of Metaplexis japonica (Thunb.) Makino and its inhibition of proliferation of human tongue cancer Tca8113 cells were studied. Method:The total alkaloids from fruit shell of Metaplexis japonica (Thunb.) Makino was extracted by alcohols. Single alkaloid compound was isolated and purified by silica gel column chromatography.Its chemical structure was analyzed by NMR and MS. The inhibition rate of alkaloids on cell proliferation was determined by MTT assay colorimetry. Cell morphology was observed by Hoechst 33342 staining. Result:Three alkaloids, secu'amamine D, securinine and securitinine, were isolated from fruit shell of Metaplexis japonica (Thunb.) Makino. MTT results showed that three alkaloids could significantly inhibit the proliferation of Tca8113 cells. Hoechst 33342 staining showed that three alkaloids could induce apoptotic morphological changes in Tca8113 cells, and positively correlated with the concentration. Conclusion:For the first time, three alkaloids, secu'amamine D, securinine and securitinine, were isolated from fruit shell of Metaplexis japonica (Thunb.) Makino. The three alkaloids inhibited the proliferation of Tca8113 cells and promoted apoptosis.